Fixed Cutter Drill Bits with Mechanically Attached Cutter Element Assemblies

This application claims benefit of U.S. provisional patent application Ser. No. 63/642,702 filed May 4, 2024, and entitled “Fixed Cutter Drill Bits with Mechanically Attached Cutter Element Assemblies,” which is hereby incorporated herein by reference in its entirety for all purposes.

Not applicable.

The present disclosure relates generally to earth-boring bits used to drill a borehole for the ultimate recovery of oil, gas or minerals. More particularly, the present disclosure relates to fixed cutter drill bits with mechanical attached cutter elements, as well as to methods of making the same and methods of using the same.

An earth-boring drill bit is typically mounted on the lower end of a drill string and is rotated by rotating the drill string at the surface or by actuation of downhole motors or turbines, or by both methods. With weight applied to the drill string, the rotating drill bit engages the earthen formation and proceeds to form a borehole along a predetermined path toward a target zone. The borehole thus created has a diameter generally equal to the diameter or “gage” of the drill bit.

Fixed cutter bits, also known as rotary drag bits, are one type of drill bit commonly used to drill boreholes. Fixed cutter bit designs include a plurality of blades angularly spaced about a bit face. The blades generally project radially outward along the bit face and form flow channels therebetween. Cutter elements are typically grouped and mounted on the blades. The configuration or layout of the cutter elements on the blades may vary widely, depending on a number of factors. One of these factors is the formation itself, as different cutter element layouts engage and cut the various strata with differing results and effectiveness.

The cutter elements disposed on the several blades of a fixed cutter bit are typically formed of extremely hard materials and include a layer of polycrystalline diamond (“PCD”) material. In the typical fixed cutter bit, each cutter element includes an elongate and generally cylindrical support member that is received and secured in a pocket formed in the surface of one of the several blades. In addition, each cutter element typically has a hard cutting layer of polycrystalline diamond or other superabrasive material such as cubic boron nitride, thermally stable diamond, polycrystalline cubic boron nitride, or ultrahard tungsten carbide (meaning a tungsten carbide material having a wear-resistance that is greater than the wear-resistance of the material forming the substrate), as well as mixtures or combinations of these materials. The cutting layer is mounted to one end of the corresponding support member, which is typically formed of tungsten carbide.

While the bit is rotated, drilling fluid is pumped through the drill string and directed out of the face of the drill bit. The fixed cutter bit typically includes nozzles or fixed ports spaced about the bit face that serve to inject drilling fluid into the passageways between the several blades. The drilling fluid exiting the face of the bit through nozzles or ports performs several functions. In particular, the fluid removes formation cuttings (for example, rock chips) from the cutting structure of the drill bit. Otherwise, accumulation of formation cuttings on the cutting structure may reduce or prevent the penetration of the drill bit into the formation. In addition, the fluid removes formation cuttings from the bottom of the hole. Failure to remove formation materials from the bottom of the hole may result in subsequent passes by cutting structure to essentially re-cut the same materials, thereby reducing the effective cutting rate and potentially increasing wear on the cutting surfaces of the cutter elements. The drilling fluid flushes the cuttings removed from the bit face and from the bottom of the hole radially outward and then up the annulus between the drill string and the borehole sidewall to the surface. Still further, the drilling fluid removes heat, caused by contact with the formation, from the cutter elements to prolong cutter element life.

Embodiments of fixed cutter drill bits for drilling earthen formations are disclosed herein. In one embodiment, a fixed cutter drill bit for drilling an earthen formation has a central axis and a cutting direction of rotation about the central axis. The drill bit comprises a bit body configured to rotate about the central axis in the cutting direction of rotation. The bit body includes a bit face and a blade extending radially along the bit face. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side. The blade includes a socket extending from the leading side of the blade and penetrating the cutter-supporting surface of the blade. The socket has a central axis, an open end at the leading side of the blade, and a closed end distal the leading side of the blade. The socket has (i) a first width Win a front view of the blade measured parallel to a projection of the cutter-supporting surface across the socket in the front view at a first distance Dmeasured perpendicular to the projection of the cutter-supporting surface in the front view, and (ii) a second width Win a front view of the blade measured parallel to the projection of the cutter-supporting surface across the socket in the front view at a second distance Dmeasured perpendicular to the projection of the cutter-supporting surface in the front view. The second distance Dis greater than the first distance Dand the second width Wat the second depth Dis greater than the first width Wat the first width W. The drill bit also comprises a cutter element assembly mounted to the blade and extending from the cutter-supporting surface of the blade. The cutter element assembly comprises a cutter element carrier seated in the socket and fixably attached to the blade. The cutter element carrier includes a base having a central axis, a leading face proximal the leading side of the blade, and a trailing face distal the leading side of the blade. The base mates with the socket. In addition, the cutter element assembly comprises a cutter element fixably attached to the cutter element carrier.

In another embodiment, a fixed cutter drill bit for drilling an earthen formation has a central axis and a cutting direction of rotation about the central axis. The drill bit comprises a bit body configured to rotate about the central axis in the cutting direction of rotation. The bit body includes a bit face and a blade extending radially along the bit face. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side. The blade includes a socket extending from the leading side of the blade and penetrating the cutter-supporting surface of the blade. Te socket has a central axis, an open end at the leading side of the blade, and a closed end distal the leading side of the blade. The socket is defined by a base surface of the blade extending axially relative to the central axis of the socket from the leading side of the blade, a first lateral side surface extending axially relative to the central axis of the socket from the leading side of the blade, and a second lateral side surface extending axially relative to the central axis of the socket from the leading side of the blade. The base surface of the blade is distal the cutter-supporting surface. The first lateral side surface and the second lateral side surface are disposed on opposite lateral sides of the central axis of the socket. Each lateral side surface extends from the cutter-supporting surface to the base surface of the blade. The first lateral side surface of the blade includes at least a portion that slopes or curves away from at least a portion of the second lateral side surface of the blade moving away from the cutter-supporting surface to toward the base surface of the blade in a front view of the blade. In addition, the drill bit comprises a cutter element assembly removably mounted to the blade and extending from the cutter- supporting surface of the blade. The cutter element assembly comprises a cutter element carrier seated in the socket and fixably attached to the blade. The cutter element carrier includes a base having a central axis, a leading end proximal the leading side of the blade, and a trailing end distal the leading side of the blade. The base of the cutter element carrier mates with the socket and has an outer surface comprising a cutter element facing surface extending axially relative to the central axis of the base from the leading end of the base to the trailing end of the base, a first lateral side surface extending axially relative to the central axis of the base from the leading end of the base to the trailing end of the base, and a second lateral side surface extending axially relative to the central axis of the base from the leading end of the base to the trailing end of the base. The blade facing surface of the base slidingly engages the base surface of the blade, the first lateral side surface of the base engages the first lateral side surface of the blade, and the second lateral side surface of the base engages the second lateral side surface of the blade. The cutter element assembly also comprises a cutter element fixably attached to the cutter element carrier.

Embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical characteristics of the disclosed embodiments in order that the detailed description that follows may be better understood. The various characteristics and features described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes as the disclosed embodiments. It should also be realized that such equivalent constructions do not depart from the spirit and scope of the principles disclosed herein.

The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct engagement between the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a particular axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to a particular axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. Any reference to up or down in the description and the claims is made for purposes of clarity, with “up”, “upper”, “upwardly”, “uphole”, or “upstream” meaning toward the surface of the borehole and with “down”, “lower”, “downwardly”, “downhole”, or “downstream” meaning toward the terminal end of the borehole, regardless of the borehole orientation. As used herein, the terms “approximately,” “about,” “substantially,” and the like mean within 10% (i.e., plus or minus 10%) of the recited value. Thus, for example, a recited angle of “about 80 degrees” refers to an angle ranging from 72 degrees to 88 degrees.

Drill bits are typically made in a manufacturing plant or factory. From the plant or factory, the drill bits are transported to the field for use. When worn, bits are typically transported to a repair center or back to the originating factory for maintenance, repair, and/or replacement. During maintenance, the bits are heated, and the cutter elements are rotated and/or replaced. After maintenance, the drill bits are then transported back to field for further use. This “lifecycle” of drill bits includes wasteful, non-value-added activities, such as transport time from and back to the field, and the associated costs. During such non-value-added activities, bits are not being used in a way that generates revenue, but instead, are idle (e.g., while being transported).

During maintenance, matrix bit bodies are susceptible to cracking when heated due to the thermal mismatch of the interior steel core (for attaching the threaded pin) and the matrix bit body. Additionally, when bits are heated, the cutter elements may sustain thermal damage, which often results in loss of wear resistance, and in extreme cases, cracking. Furthermore, when the drill bits are heated and cutter elements are brazed, there is a risk of human error that the drill bit will be overheated or a cutter element will be placed directly into an acetylene flame, thereby potentially causing thermal damage. It should also be appreciated that a considerable amount of time is required to heat and braze cutter elements into a drill bit, and still further time is necessary after heating the drill bit to clean the bit (e.g., remove flux in a bath). Subsequent to such heating and cleaning, the drill bits are blasted (e.g., to remove excess braze) and then dye checked for potential cracks in the bit body and/or cutter elements.

Moreover, cutter elements mounted to the blades of fixed cutter drill bits typically extend from the formation facing surfaces of the blades to an extension height measured perpendicularly from the formation facing surface. In general, a greater extension height allows for increased depth-of-cut into the formation during drilling and increased rate-of-penetration (ROP) of the drill bit during drilling. Most conventional cutter elements, which are directly brazed into mating pockets formed in the blades, are typically limited to extension heights equal to about 50% of the diameter of the cutting faces of the cutter elements. Such limitation is due, at least in part, to the strength of the connections (e.g., the brazed bond) between the cutter elements and the blades, as well as the fact that the cutter elements are directly attached to the blades.

For at least the foregoing reasons, there exists a need for drill bits than can be maintained and repaired more efficiently, cutter elements that can be mounted to blades with reduced risk of thermal damage, and cutter elements that can be mounted to the blades with sufficient attachment strengths to enable increased extension heights. Accordingly, embodiments described herein are directed to drill bits including cutter elements that are mechanically coupled to the blades extending from the bit bodies, cutter elements that can be mounted to blades with reduced risk of thermal damage, and cutter elements that can be mounted at greater extension heights. In some embodiments, the blades are configured for relatively quick removal and attachment of cutter elements. As a result, rather than require transport to a factory or repair center, a field office can be positioned in the field for rapid drill bit build customization, repair, and maintenance. In other words, the drill bits and cutter elements thereon can be repaired, maintained, and replaced (as desired) on site, without transport over long distances (after initial delivery to the field). In some embodiments disclosed herein, the cutter elements can be replaced at the field location without requiring heating of the bit, which requires time for both heating and cooling of the bit, as well as presents the risk of thermal damage to the cutter elements. Further, the cutter elements can be brazed in a controlled, lab environment separate from the bit, thereby avoiding the time required need to heat and cool the entire drill bit, increasing the speed of the brazing process, reducing the propensity for thermal damage to the cutter elements, and reducing the amount of time the cutter elements are exposed to a deleterious oxygen containing atmosphere at elevated temperatures.

Referring now to, a schematic view of an embodiment of a drilling systemin accordance with the principles described herein is shown. Drilling systemincludes a derrickhaving a floorsupporting a rotary tableand a drilling assemblyfor drilling a boreholefrom derrick. Rotary tableis rotated by a prime mover such as an electric motor (not shown) at a desired rotational speed and controlled by a motor controller (not shown). In other embodiments, the rotary table (for example, rotary table) may be augmented or replaced by a top drive suspended in the derrick (for example, derrick) and connected to the drillstring (for example, drillstring).

Drilling assemblyincludes a drillstringand a drill bitcoupled to the lower end of drillstring. Drillstringis made of a plurality of pipe jointsconnected end- to-end, and extends downward from the rotary tablethrough a pressure control device, such as a blowout preventer (BOP), into the borehole. The pressure control deviceis commonly hydraulically powered and may contain sensors for detecting certain operating parameters and controlling the actuation of the pressure control device. Drill bitis rotated with weight-on-bit (WOB) applied to drill the boreholethrough the earthen formation. Drillstringis coupled to a drawworksvia a kelly joint, swivel, and linethrough a pulley. During drilling operations, drawworksis operated to control the WOB, which impacts the rate-of-penetration of drill bitthrough the formation. In this embodiment, drill bitcan be rotated from the surface by drillstringvia rotary tableor a top drive, rotated by downhole mud motordisposed along drillstringproximal bit, or combinations thereof (for example, rotated by both rotary tablevia drillstringand mud motor, rotated by a top drive and the mud motor, etc.). For example, rotation via downhole motormay be employed to supplement the rotational power of rotary table, if required, or to effect changes in the drilling process. In either case, the rate-of-penetration (ROP) of the drill bitinto the boreholefor a given formation and a drilling assembly largely depends upon the WOB and the rotational speed of bit.

During drilling operations, a suitable drilling fluidis pumped under pressure from a mud tankthrough the drillstringby a mud pump. Drilling fluidpasses from the mud pumpinto the drillstringvia a desurger, fluid line, and the kelly joint. The drilling fluidpumped down drillstringflows through mud motorand is discharged at the borehole bottom through nozzles in face of drill bit, circulates to the surface through an annular spaceradially positioned between drillstringand the sidewall of borehole, and then returns to mud tankvia a solids control systemand a return line. Solids control systemmay include any suitable solids control equipment known in the art including, without limitation, shale shakers, centrifuges, and automated chemical additive systems. Control systemmay include sensors and automated controls for monitoring and controlling, respectively, various operating parameters such as centrifuge rpm. It should be appreciated that much of the surface equipment for handling the drilling fluid is application specific and may vary on a case-by-case basis.

Referring now to, drill bitis a fixed cutter bit, sometimes referred to as a drag bit, and is designed for drilling through formations of rock to form a borehole. Bithas a central or longitudinal axis, a first or uphole end, and a second or downhole end. Bitrotates about axisin the cutting direction represented by arrow. In addition, bitincludes a bit bodyextending axially from downhole end, a threaded connection or pinextending axially from uphole end, and a shankextending axially between pinand body. Pincouples bitto a drill string (not shown), which is employed to rotate the bitin order to drill the borehole. Bit body, shank, and pinare coaxially aligned with axis, and thus, each has a central axis coincident with axis.

The portion of bit bodythat faces the formation at downhole endincludes a bit faceprovided with a cutting structure. Cutting structureincludes a plurality of blades that extend from bit face. As best shown in, in this embodiment, cutting structureincludes three angularly spaced-apart primary bladesand three angularly spaced apart secondary blades. Further, in this embodiment, the plurality of blades (for example, primary blades, and secondary blades) are uniformly angularly spaced on bit faceabout bit axis. In particular, the three primary bladesare uniformly angularly spaced about 120° apart, the three secondary bladesare uniformly angularly spaced about 120° apart, and each primary bladeis angularly spaced about 60° from each circumferentially adjacent secondary blade. In other embodiments, one or more of the blades may be spaced non-uniformly about bit face. Still further, in this embodiment, the primary bladesand secondary bladesare circumferentially arranged in an alternating fashion. In other words, one secondary bladeis disposed between each pair of circumferentially-adjacent primary blades. Although bitis shown as having three primary bladesand three secondary blades, in general, bitmay comprise any suitable number of primary and secondary blades. As one example only, bitmay comprise two primary blades and four secondary blades.

Referring still to, in this embodiment, primary bladesand secondary bladesare integrally formed as part of, and extend from, bit bodyand bit face. Primary bladesand secondary bladesextend generally radially along bit faceand then axially along a portion of the periphery of bit. In particular, primary bladesextend radially from proximal central axistoward the periphery of bit body. Primary bladesand secondary bladesare separated by drilling fluid flow courses. Each blade,has a leading edge or side,, respectively, and a trailing edge or side,, respectively, relative to the direction of rotationof bit.

Each blade,includes a cutter-supporting surfacethat generally faces the formation during drilling and extends circumferentially from the leading sideto the trailing sideof the corresponding blade,. During drilling operations, cutter-supporting surfacegenerally faces the surrounding formation, and thus, may also be referred to herein as formation-facing surface. In this embodiment, a plurality of cutter element assembliesare fixably attached to each blade,and extend from cutter-supporting surfaceof each blade,. Cutter element assembliesare generally arranged adjacent one another in a radially extending row proximal the leading sideof each primary bladeand each secondary blade. However, in other embodiments, the cutter element assemblies (for example, cutter element assemblies) may be arranged differently.

As will be described in more detail below, each cutter element assemblyincludes a cutter element carrierfixably mounted to the corresponding blade,and a cutter elementfixably secured to and carried by the carrier. Although cutter element assembliesare fixably mounted to blades,, and thus, do not move rotationally or translationally during drilling operations, cutter element assembliesare mechanically attached to blades,such that any one or more cutter element assembliescan be independently removed for repair, maintenance, or replacement. Accordingly, drill bit, as well as other embodiments of drill bits described herein, may be referred to as “modular;” and further, cutter element assemblies, as well as other embodiments of cutter element assemblies described herein, may be referred to as removably attached or secured to the blades.

As will be described in more detail below, each cutter elementincludes an generally cylindrical support base or substrateand a cylindrical disk or tablet-shaped, hard cutting layerbonded to the exposed end of substrate. Substrateis typically made of a carbide material such as tungsten carbide, whereas cutting layeris typically made of polycrystalline diamond or other superabrasive material. Substratehas a central axis, and as will be described in more detail below, is received and secured in a pocket formed in the corresponding carrier, which in turn is fixably received by and secured to the corresponding blade,to which it is mounted. The cylindrical disc, hard cutting layerdefines a cutting faceof the corresponding cutter element. In this embodiment, each cutting faceis the same and is planar. However, in other embodiments, one or more cutting faces (e.g., cutting faces) may not be completely planar, but rather, be non-planar. As used herein, the phrase “non-planar” may be used to refer to a cutting face that includes one or more curved surfaces (for example, concave surface(s), convex surface(s), or combinations thereof), a plurality of distinct planar surfaces that intersect at distinct edges along the cutting face, or both. In this embodiment, some cutter elements, which are also labeled with reference numeral′, may be directly attached to the cutter-supporting surfaceof the corresponding blade,without a corresponding carrier.

In the embodiments described herein, each cutter element assemblyis mounted such that the central axisof the corresponding cutter elementis oriented substantially parallel to or at an acute angle relative to the cutting direction of the bit (for example, cutting directionof bit). Such orientation results in the corresponding cutting facebeing generally forward-facing relative to the cutting direction of the bit (for example, cutting directionof bit). The point or portion of cutting faceof each cutter elementpositioned furthest from the cutter-supporting surfaceof the corresponding blade,as measured perpendicular to the corresponding cutter-supporting surfacedefines a cutting tipof cutting face.

Referring still to, bit bodyfurther includes gage padsof substantially equal axial length measured generally parallel to bit axis. Gage padsare circumferentially-spaced about the radially outer surface of bit body. Specifically, one gage padintersects and extends from each blade,. In this embodiment, gage padsare integrally formed as part of the bit body. In general, gage padscan help maintain the size of the borehole by a rubbing action when cutter element assemblieswear slightly under gage. Gage padsalso help stabilize bitagainst vibration.

Referring now to, an exemplary profile of blades,is shown as it would appear with blades,and cutting facesrotated into a single rotated profile. In rotated profile view, blades,form a combined or composite blade profilegenerally defined by cutter-supporting surfacesof blades,. In this embodiment, the profiles of surfacesof blades,are generally coincident with each other, thereby forming a single composite blade profile.

Composite blade profileand bit facemay generally be divided into three regions conventionally labeled cone region, shoulder region, and gage region. Cone regionis the radially innermost region of bit bodyand composite blade profilethat extends from bit axisto shoulder region. In this embodiment, cone regionis generally concave. Adjacent cone regionis generally convex shoulder region. The transition between cone regionand shoulder region, referred herein to as the nose, occurs at the axially outermost portion of composite blade profile(relative to bit axis) where a tangent line to the blade profilehas a slope of zero. Moving radially outward, adjacent shoulder regionis the gage region, which extends substantially parallel to bit axisat the outer radial periphery of composite blade profile. As shown in composite blade profile, gage padsdefine the gage regionand the outer radius Rof bit body. Outer radius Rextends to and therefore defines the full gage diameter of bit.

Referring briefly to, moving radially outward from bit axis, bitand bit faceinclude cone region, shoulder region, and gage regionas previously described. Primary bladesextend radially along bit facefrom within cone regionproximal bit axistoward gage regionand outer radius R. Secondary bladesextend radially along bit facefrom proximal nosetoward gage regionand outer radius R. Thus, in this embodiment, each primary bladeand each secondary bladeextends substantially to gage regionand outer radius R. In this embodiment, secondary bladesdo not extend into cone region, and thus, secondary bladesoccupy no space on bit facewithin cone region. Although a specific embodiment of bit bodyhas been shown in described, one skilled in the art will appreciate that numerous variations in the size, orientation, and locations of the blades (for example, primary blades, secondary blades,, etc.), and cutter elements (for example, cutter element assemblies) are possible.

Bitincludes an internal plenum extending axially from uphole endthrough pinand shankinto bit body. The plenum allows drilling fluid to flow from the drill string into bit. Bodyis also provided with a plurality of flow passages extending from the plenum to downhole end. As best shown in, a nozzleis seated in the lower end of each flow passage. Together, the plenum, passages, and nozzlesserve to distribute drilling fluid around cutting structureto flush away formation cuttings and to remove heat from cutting structure, and more particularly cutter element assemblies, during drilling.

Referring again to, on each blade,, cutter element assembliesare arranged side-by-side in a row along the corresponding cutter-supporting surfaceproximal leading side,. Thus, in this embodiment, cutter element assembliesare positioned radially adjacent one another on a given blade,. However, in other embodiments, the cutter element assemblies (for example, cutter element assemblies) may be arranged in rows with one or more cutter element having a different geometries on the same blade (for example, blade,).

Referring now to, enlarged views of one exemplary bladeare shown. In, cutter element assembliesare shown mounted to blade, however, in, cutter element assembliesare removed. Although one exemplary primary bladeis shown inand will be described, it is to be understood that the other primary bladesand secondary bladesare generally the same.

Bladeincludes a plurality of radially adjacent recesses or socketsfor receiving cutter element assemblies, and in particular, receiving mating cutter element carriersof cutter element assemblies. Each socketextends into the bladegenerally perpendicularly from leading sideand cutter-supporting surface. Thus, each socketintersects and extends through leading side, cutter-supporting surface, and the convex edge between the corresponding cutter-supporting surfaceand leading side

Referring now to, one socketwill be described it being understood the other socketsare the same. Sockethas a central or longitudinal axis, a first or open endat leading side, and a second or closed endopposite endand distal the leading side. Central axisis oriented parallel to central axisof substrateof the corresponding cutter elementand parallel to cutting directionof bitat the radial position of the corresponding cutter element. Open endis positioned forward of and leads closed endrelative to relative to cutting directionof bit. Accordingly, open endmay also be referred to as leading endand closed endmay also be referred to as trailing end

Referring still to, socketis defined by generally trapezoidal profile projected into bladefrom leading sideand open endto trailing endin a direction parallel to central axis. Thus, each cross-section of sockettaken in a plane oriented perpendicular to axisgenerally has the same size, shape, and trapezoidal geometry. As best shown in, in this embodiment, socketis generally symmetric about a reference plane R (illustrated with a dashed line in) oriented perpendicular to a projection Pof cutter-supporting surfaceacross socket(illustrated with the dotted line in) and containing central axisin front view of the bladealong axis. However, in other embodiments, the socket (e.g., socket) is not symmetric about a plane (e.g., reference plane R).

Socketis defined by a plurality of surfaces formed by the surrounding bladeincluding a base surfaceextending axially (relative to axis) from open endto closed end, a pair of lateral side surfacesextending axially (relative to axis) from open endto closed end, and a rear support surfacedefining closed end. In this embodiment, a cutter element assembly supportintegral with bladeextends from cutter-supporting surfaceat trailing endof socketand defines a portion of rear support surfaceextending axially (relative to bit axis) from cutter-supporting surface. As will be described in more detail below, cutter element assembliesare received into mating socketswith cutter element carriersslidingly engaging surfaces,,.

In this embodiment, base surfaceis a planar surface oriented parallel to central axis, parallel to cutter-supporting surface, and perpendicular to leading side. Base surfaceextends laterally between side surfaces. In addition, base surfaceis distal cutter-supporting surfaceand spaced therefrom. As best shown in, a counterboreextends perpendicularly from base surfaceinto blade.

Referring again to, lateral side surfacesare laterally spaced apart (on opposite sides of central axis), and in this embodiment, are planar surfaces oriented parallel to central axisand extend perpendicularly from leading side. Lateral side surfacesare disposed along opposite lateral sides of base surfaceand generally extend from base surfaceto cutter-supporting surface. In this embodiment, a concave (bowed inwardly) rounded transition surface is provided between base surfaceand each lateral side surface, and a convex (bowed outwardly) rounded transition surface is provided between each lateral side surfaceand cutter-supporting surfaceof blade.

Lateral side surfacesgenerally slope or taper away from each other moving from cutter-supporting surfaceto base surface. Stated differently, lateral side surfacesgenerally slope or taper toward from each other moving base surfaceto cutter-supporting surface. In particular, as shown in, each lateral side surfaceis oriented at an angle a relative to the reference plane R. In embodiments described herein, each angle α ranges from 0° to 90°, and preferably ranges from 25° to 75°. As lateral side surfacesgenerally taper away from each other moving perpendicularly from the projection Pof cutter-supporting surface, surfacesmay be described as negative draft surfaces, and further, each angle α may be described as being a negative draft angle. In this embodiment, each lateral side surfaceis oriented at the same angle α, and in particular, the angle α of each lateral side surfaceis 55°.

Referring still to, sockethas a width Win front view of the corresponding blade,(as viewed perpendicular to leading side,along central axisas shown in) measured (i) parallel to the projection Pof cutter-supporting surface, and (ii) perpendicular to the reference plane R. As lateral side surfacesgenerally taper away from each other moving perpendicularly to the projection Pof cutter-supporting surface, the width Wgenerally increases moving from the projection Pof cutter-supporting surfacetoward base surface. Stated differently, socketmay be described as having a first width Wat a first depth or distance Dmeasured perpendicularly from the projection Pof cutter-supporting surface, a second width Wat a second depth or distance Dmeasured perpendicularly from the projection Pof cutter-supporting surfacethat is greater than the first depth D, where second width W(at the greater depth D) is greater than the first width W(at the lesser depth D). Accordingly, socketmay be described as having a “dovetail” shape or geometry in a front view of the blade. It should be appreciated that such geometry generally resists and/or prevents mating cutter element carrier(and hence cutter element assembly) from being pulled or removed from socketin a direction perpendicular to the projection Pof cutter-supporting surface(i.e., upwardly as shown in).

Although lateral side surfacesare planar surfaces that continuously slope away from each other moving perpendicularly from cutter-supporting surfacein this embodiment, in other embodiments, the lateral side surfaces (e.g., side surfaces) may not be planar and/or may not continuously slope away from each other. However, in embodiments described herein, each socket (e.g., each socket) preferably has a first width measured at a first depth (e.g., a first depth W) measured perpendicularly from the cutter-supporting surface (e.g., cutter-supporting surface), a second width (e.g., a first depth W) at a second depth measured perpendicularly from the cutter-supporting surface that is greater than the first depth, where the second width (at the greater depth) is greater than the first width (at the lesser depth) such that the geometry of the socket and mating cutter element carrier (e.g., carrier) generally resist and/or prevent the cutter element carrier and associated cutter element assembly (e.g., cutter element assembly) from being pulled or removed from the socket in a direction perpendicular to cutter-supporting surface.

Referring again to, rear support surfaceis disposed at closed endand extends axially (relative to bit axis) from base surfacealong bladeand support. In addition, rear support surfaceextends laterally (relative to central axis) between lateral side surfaces. In this embodiment, a concave (bowed inwardly) rounded transition surface is provided between base surfaceand rear support surface, and a concave (bowed inwardly) rounded transition surface is provided between rear support surfaceand each lateral side surface. In this embodiment, rear support surfaceis a planar surface oriented perpendicular to base surface, cutter-supporting surface, central axis, and cutting directionof bit.

Referring now to, one cutter element assemblywill be described it being understood that each cutter element assemblyis the same. As previously described, cutter element assemblyincludes cutter element carrierand cutter elementfixably mounted and secured thereto. As also previously described, each cutter elementincludes cylindrical substrateand cylindrical hard cutting layerbonded to substrate. Each substratehas a central axis, and each cutting layerdefines a cutting face. More specifically, each cutter elementhas a leading endrelative to cutting directionof bit, a trailing endaxially opposite end(relative to axis), and a radially outer surfaceextending axially from leading endto trailing end. Cutting faceis disposed at leading end. Trailing endcomprises a planar surface. In this embodiment, cutting faceand planar surfaceare disposed in planes oriented perpendicular to axis. Outer surfaceincludes a cylindrical surfaceextending axially from leading endto trailing endalong both cutting layerand substrate. In this embodiment, outer surfacealso includes a pair of circumferentially-spaced flatsextending along cylindrical surfacefrom leading endto trailing end. Cutting tipis circumferentially positioned between flatsat the intersection of cutting faceand cylindrical surface. Cutter elementalso includes a sloped indexing flat(illustrated with hidden lines in) extending radially inward and axially rearward (relative to axis) from outer surfaceto planar surface. Sloped indexing flatis angularly spaced 180° from cutting tipadjacent trailing end

Referring now to, cutter element carrierhas a first endand a second endopposite end. When cutter element assemblyis seated in a mating socket, first endis positioned forward of and leads second endrelative to the cutting directionof bit. Accordingly, first endmay also be referred to as leading end, and second endmay also be referred to as trailing end

Cutter element carrieris generally L-shaped, monolithic member in side view. In particular, cutter element carrierincludes a baseextending from leading endto trailing endand a cutter element support blockextending from baseat trailing end. As a result, baseand support blockdefine a receptacle or pocketextending axially from leading endof cutter element carrierto support block. Pocketis sized to receive and mate with cutter element.

As best shown in, basehas a central or longitudinal axis, a leading faceat end, and a trailing faceat end. In addition, basehas an outer surface including a blade facing surfaceextending axially (relative to axis) from leading endto trailing end, a pair of lateral side surfacesextending axially (relative to axis) from leading faceto trailing face, and a cutter element facing surfaceextending axially (relative to axis) from leading faceto support block. Blade facing surfaceand cutter element facing surfaceare radially spaced apart (relative to axis), and each extends laterally (relative to axis) between lateral side surfaces. Thus, lateral side surfacesare disposed along opposite lateral sides of blade facing surfaceand extend from blade facing surfaceto cutter element facing surfacealong pocket, and extend from blade facing surfaceto support blockrearward of pocket.

In this embodiment, leading faceand trailing faceare defined by planar surfaces oriented perpendicular to central axis, blade facing surfaceis a planar surface oriented parallel to central axis, and lateral side surfacesare laterally spaced planar surfaces (on opposite sides of axis) oriented parallel to central axis. Blade facing surfaceof carrierslidingly engages and is flush with mating base surfaceof socket, and lateral side surfacesof carrierslidingly engage and are flush with mating lateral side surfacesof socket. Thus, as best shown in, the outer surface of baseis sized and shaped to mate with a corresponding socketand slidingly engage surfaces,defining socketas shown in. In other words, basehas a geometry that is the same as socket. Namely, basehas a generally trapezoidal profile extending from leading faceto trailing facein a direction parallel to central axis. Thus, each cross-section of basetaken in a plane oriented perpendicular to axisgenerally has the same size, shape, and trapezoidal geometry. As previously described, in this embodiment, socketis symmetric about the reference plane R in front view of the blade(), and thus, in this embodiment, mating baseis also symmetric about the reference plane R when baseis seated in socket. However, in other embodiments, the base of the cutter element carrier (e.g., baseof carrier) may not be symmetric about a reference plane (e.g., reference plane R).